An application sends an EM_SETSEL message to select a range of characters in an edit control.
EM_SETSEL wParam = (WPARAM) (INT) nStart; // starting position lParam = (LPARAM) (INT) nEnd; // ending position
This message does not return a value.
In a rich edit control, if the selection is not entirely contained in the first 64K, use the message EM_EXSETSEL.
If the nStart parameter is 0 and the nEnd parameter is -1, all the text in the edit control is selected. If nStart is -1, any current selection is removed. The caret is placed at the end of the selection indicated by the greater of the two values nEnd and nStart.
In previous versions of Windows, the wParam parameter is a flag that is set to FALSE to scroll the caret into view or set to TRUE to omit the scrolling. A Win32-based application should use the EM_SCROLLCARET message to scroll the caret into view.
In earlier versions of Windows, the starting and ending positions of the selection are indicated by the low- and high-order words, respectively, of the lParam parameter.